Electrical control device for a hydraulic circuit



J. PIRET 3,489,063

ELECTRICAL CONTROL DEVICE FOR A HYDRAULIC CIRCUIT Jan. 13, 1970 FiledNOV; 24, 1967 Q1 \B oo llo Fm w Illa F United States Patent 5 05 Int.Cl. F01] 25/08:- Fb 13/16, 13/04 US. Cl. 91275 4 Claims ABSTRACT OF THEDISCLOSURE A device for controlling a hydraulic circuit which comprisesa source of pressurized fluid, a pressure regulator controlling themaximum pressure of the source of pressurized fluid, a cylinder having adouble-acting reciproeating piston, a distributor selectively connectingthe source of pressurized fluid to the cylinder and a return conduit, apair of electromagnets mounted at each end of the distributor, controlcircuit means for the electromagnets including a pair of end of travelswitches and a change of direction switch, the end of travel switchesand the change of direction switch being controlled by the piston, asecond pair of switches each of which has at least two sets of contacts,the second pair of switches being operated by the movement of thecorresponding electromagnet by the intermediary of a mechanicaltransmission cooperating with the distributor, one of each of the twosets of contacts of the second pair of switches is placed in the supplycircuit of each of the electromagnets so that only one of theelectromagnets can be energized at a time.

The present invention relates to an electric control device forhydraulically controlling a double-acting piston, and particularly todevices of this type in which the hydraulic piston is actuated by afluid which controls a machine-tool.

It is well known that in order to achieve the alternating displacementof a mechanical element such as a tool holder, a pressure plate, or amechanical shovel, a hydraulic circuit which acts alternately on thedoubleacting piston of a cylinder, may be used. The piston being rigidlyconnected to the element to be displaced.

The simplest hydraulic circuits usually associated with double-actingcylinders having two chambers are in general constituted by a source ofhydraulic fluid under pres sure such as a pump which draws fluid from areservoir, a pressure regulator in the delivery line of the pump and adistributor mounted in the delivery line downstream of the pressureregulator and upstream of the cylinder. This distributor beingadjustable into three positions so as to establish the followingconnections: in a first end position of the distributor, the leftchamber of the cylinder is connected with the delivery conduit of thepump and the right chamber of the cylinder is connected with a reservoirreturn conduit; in a second or intermediate position of the distributor,the two chambers of the cylinder are connected with the delivery conduitand the reservoir return conduit; and in the other end position, theright chamber of the cylinder is connected with the pump deliveryconduit and the left chamber is connected with the reservoir returnconduit.

An electric control for this type of a hydraulic circuit normallycomprises: two electromagnets one of which is connected to each side ofthe distributor. These electromagnets act on the distributor in adirection opposite to each other so as to urge the distributor from theintermediate position into one of its end positions. The electriccontrol also includes an electrical circuit for controlling theseelectromagnets and includes two end of travel switches and one travelreversing switch. The three switches are controlled by a cam carried bythe rod of the piston mounted in the cylinder. The electric circuitfurther includes two relay connected to the electromagnets by a delayswitch utilized to delay the excitation of the second electromagnetuntil after the de-excitation of the first electromagnet.

The known electrical devices are normally placed in a protective housingprovided beside the machine-tool and always require connecting electriccables or wires for the different electrical elements contained in thehousing. In this type of an installation the electromagnets must beprovided with cables which can handle the excitation current thereof,which is much higher than the intensity of the circuit current utilizedby the relays and the switches. Furthermore, the relays are usuallyfairly expensive which adds considerably to the cost of theinstallation. Also, since the excitation and de-excitation of theelectromagnets is not only a function of the position of the piston inthe cylinder by means of the cam and the switches at the finish of astroke, but also of the delay switch, the operation of the device is notexact.

The present invention eliminates all of these inconveniences byproviding an electrical control means for a hydraulic circuit of thetype mentioned above which does away with all relays and therequirements for a separate protective housing and which controls thefeeding of the electromagnets as a function of the position of thedistributor.

In this way, it is possible to eliminate the relays and the largeprotective housing and to control the feeding of the electromagnets as afunction of the position of the slide valve in the distributor, thusassuring a highly exact control of the hydraulic circuit.

These and other objects of the present invention will become morereadily understood from the following description of an embodiment ofthe invention, given only by way of example, together with the attacheddrawing in which:

FIG. 1 is a schematic representation of a hydraulic operating circuitfor a piston and an electrical control device for this hydrauliccircuit; and

FIG. 2 is a schematic representation of an electrical control device inaccordance with this invention.

Referring now to FIG. 1, there is shown a cylinder 1, for use with amachine tool sealingly carrying a piston 2 therein. A piston rod 3 isintegrally formed at one end with the piston 2 and carries at its freeend a earn 4. Two chambers 5 and 6 are formed on either side of thepiston 2 in the cylinder 1. A principal distributor 9 is connected tochamber 5 by a conduit 7 and to chamber 6 by a conduit 8. Thisdistributor 9 is constituted by a slide valve which is movable intothree positions 9a, 9b and 9c as schematically shown in FIG. 1. In thesethree positions the chambers 5 and 6 of the cylinder are selectivelyconnected to a hydraulic delivery circuit 10 of a pump P and/or a returnconduit 11 which feeds fluid into a pump reservoir 12. e

In the intermediate or normal position 91), the distributor 9 connectsthe hydraulic delivery line 10 with the chambers 5 and 6 and thechambers 5 and 6 with the return conduit 11. In other words, theconduits 10 and 11, and the chambers 5 and 6 all communicate with eachother and there is practically no pressure in all of the elements.

In the end position 9a, shown at the left in FIG. 1 of the drawing, thedistributor 9 connects the hydraulic delivery conduit 10 with thechamber 5 and the return conduit 11 with the chamber 6.

In the other end position 9c, shown at the right in FIG. 1 of thedrawing, the distributor 9 connects the delivery conduit 10 with thechamber 6 and the return conduit 11 with the chamber 5.

A pressure regulator 13 is mounted in parallel with the delivery conduit10 and permits the maximum pressure in this conduit to be accuratelygoverned.

Two springs 14 and 15 of equal force act against opposite ends of thedistributor 9 to normally maintain this distributor in the intermediateposition 9b.

Transmission rods 16 and 17 are attached to each end of the distributor9 and cooperate with movable armatures 18 and 19, respectively, of acorresponding electromagnet A or B. The free ends of the armatures 18and 19 are provided with push rods 20 and 21, respectively. The push rod20 cooperates with one end of a hinged arm 22 which is capable of actingon a switch having two sets of contacts B and B: through the other endof the arm. The push rod 21 cooperates with a hinged arm 23 to operatethe contacts A A in the same manner. That is, the double throw switch AA is operated by the movement of the armature 18 of the electromagnet Aby means of a unidirectional mechanical transmission which comprises theslide valve of the distributor 9, the rod 17, the movable armature 19 ofthe electromagnet B, the push rod 21 and the hinged lever 23. Themovable armature 18 acts an the unidirectional mechanical transmission,only when the electromagnet A is energized.

The operation of the switch containing the contacts B B is effected inan analogous manner by the movable armature 19 of the electromagnet B bymeans of the slide valve in the distributor 9, the rod 16, push rod 20and hinged lever 22.

Each of a pair of switches containing the two sets of contacts A A and BB are subjected to the action of springs 24 and 25, respectively, whichsprings are disposed in association with the respective levers 23 and22, in such a manner that in the intermediate position 9b of thedistributor 9, the contacts A and B are closed and the contacts A and Bare open. Each of the pair of switches is housed within a fluid tighthousing 27, 28, respectively, mounted on the distributor 9.

The cam 4 cooperates with two end of travel switches F and P and achange of direction switch F These switches are disposed in such amanner that in the starting position of the piston 2, the cam 4cooperates with the switch F and in the end position of the piston shownto the right in FIG. 1, this cam cooperates with the switches F and Peg.

When the control rod of the switch F is contacted by the cam 4, it isbiased into the open position and when the common control rod of theswitches P and P is contacted by the cam 4, the switch F is opened andthe switch F is closed. The end of travel switch F is opened when thefront inclined ramps portion of the cam 4 first comes in contact withits push rod, while the opened change of direction switch remains in theopened position, until the push rod arrives on the flat top portion ofthe cam 4.

The electrical control device is supplied from a source of alternatingcurrent (not shown) via lines and 31, and comprises two electrical unitsU and U each of which is, respectively, provided with an operating coil,for the electromagnets A and B.

The different switches represented in FIG. 2 are of two types. All ofthe switches which are found on the left hand side of an electric linetaken in the direction of the arrow F are closed and the switchesindicated as being to the right of this line are opened when they arenot activated by their corresponding control elements.

The first electric unit U comprises the end of travel switch F connectedin series with a parallel assembly containing the set of contacts A amanual starting switch Ma, and an automatic cycling switch Ca. Onceoperated the automatic cycling switch Ca remains in the position inwhich it has been placed. The parallel assembly is in turn connected inseries with the contact B which is connected in series with the coil ofthe electromagnet A.

The second electric unit U includes a parallel assembly constituted bythe change of direction switch F and the end of travel switch Fconnected in series with the set of contacts B The parallel assembly ofunit 2 is connected in series with the set of contacts A which is inturn connected in series with the coil of the electromagnet B.

The operation of the device is as follows: as shown in FIGS. 1 and 2,the device rests in its normal or rest position with the electromagnetsA and B being in an unexcited position. The piston 2 is in its extremeleft position, the end of travel switch F is open, the end of travelswitch P is closed, the change of direction switch P is open, thedistributor 9 is in the intermediate position, the contacts A and B areclosed and the contacts A and B are open.

To control the displacement of the slide valve contained in thedistributor 9 and thereby displace the piston 2 from the left to theright, the starting switch Ma is closed thereby causing the excitationof the electromagnet A. The movable armature 18 moves from left to rightthereby moving the distributor 9 into its end position 9a. At the sametime, this movement is transmitted, by the intermediary of the rod 16 ofthe distributor 9 to the rod 17 and thus to the movable armature 19 ofthe electromagnet B, thereby moving the push rod 21 causing the lever 23to turn on its fulcrum first opening the contacts A and, then, closingthe contacts A The further excitation of the elcctromagnet is nowassured by the closed contacts F A and B and the manual switch Ma may bereleased.

In this end position 9a of the distributor 9, the chamber 5 of thecylinder 1 is connected to the delivery conduit 10, and the chamber 6 isconnected to the return conduit 11. The piston 2 is thus moved from theleft towards the right under the action of the fluid entering thechamber 5. At the beginning of the movement of the piston 2, the cam 4releases the push rod of switch F allowing the switch to move to theclosed position, but this closing has no instantaneous effect on thedevice. When the piston 2 arrives at the extreme right position of thecylinder 1, the inclined ramp portion of the cam 4 opens the end oftravel switch F thereby cutting-off the fiow of current to theelectromagnet A and when the push rod reaches the top portion of thecam, the switch P is closed.

When the current supply to the electromagnet A is cutoh, the springs 14and 15 bias the slide valve of the distributor into the intermediateposition 9b in which the contacts A are closed therefore allowing thecoil of the electromagnet B to be excited through the intermediary ofthe switch Fcg.

The excitation of the electromagnet B causes the displacement of themovable armature 19 of distributor 9 and of the movable armature 18 ofelectromagnet A. This movement causes the lever 22 to first open thecontacts B, and then close the contacts B when the slide valve of thedistributor 9 has been moved to the position 9c. In this position, thechamber 5 is connected to the return conduit 11 and the chamber 6 isconnected to the delivery conduit 10.

The closing of the contact B connected in parallel with the switch Fassures feeding of the coil of the electromagnet B. There is thereforeno de-excitation of the electromagnet B when the piston 2 is moved fromright to left and the cam 4 releases the push rod of the switch F toreopen it.

The closing of the switch F does not excite the electromagnet A sincethe contacts B remain open. When the piston 2 arrives at the extremeleft end position in the cylinder 1, the cam 4 opens the switch F whichcutsoff the flow of current to the electromagnet B and the springs 14and 15 bias the distributor into its intermediate position 9b. In thisposition the contacts A and B are again closed and the contacts A and Bare open.

However, the excitation of one of the electromagnets takes place onlyafter the feeding current has been cut-off to the other electromagnetsince the cut-off signal will only be observed after the slide valve ofthe distributor has started its movement towards the center. It istherefore impossible to provoke an accidental excitation of one of theelectromagnets, The contacts A A B and B; will not supply current to anelectromagnet until after a delay caused by the time required to cut olfthe other electromagnet and a predetermined movement of the distributorslide valve. In this manner, these contacts control the end of onesequence of operation of the distributor before they allow thecommencement of another sequence.

If, during a first reciprocating stroke of the piston 2, the automaticcycling switch Cu is closed, the feeding of the coil of theelectromagnet A is automatically assured by the intermediary of theswitch Ca and the contacts B which are now closed and a new cyclecommences. In the opposite case, such as shown in FIG. 2, the piston 2rests in its extreme left position.

This invention is particularly adapted to be used with switch controlsystems which are operated by a distributor or the movable armature ofan electromagnet associated with the distributor. But, the inventionalso may be applied to control systems which require the operation of apneumatic distributor having a slide valve, check valves or a rotaryvalve and for all other modes of distribution.

Also, the number of sets of contacts operating the electromagnets do nothave to be limited to two, but, if considered desired, four or more setsof contacts may be used to assure the automatic operation of a morecomplex cycle.

What is claimed is:

1. A device for the electric control of a hydraulic circuit; saidhydraulic circuit comprising: a source of pressurized fluid; a deliveryconduit for said pressurized fluid; a distributor in said deliveryconduit having a body and two ends; a cylinder having a double actingpiston connected to said distributor; electrical control means for saiddevice including: an electromagnet mounted at each end of saiddistributor and a control circuit for said electromagnets; said controlcircuit having two end of travel switches and a change of travel switch;said switches being controlled by said piston; a second pair of switcheseach of which contains two sets of contacts; each of said second pair ofswitches capable of being operated by a corresponding electromagnetthrough the intermediary of the distributor; one of the two sets ofcontacts of one of said second pair of switches being placed in a supplycircuit of one of the electromagnets and the other set of contacts beingplaced in a supply circuit of the other electromagnet.

2. A device for controlling a hydraulic circuit as recited in claim 1including a starting switch and a recycling switch in parallel, saidswitches being in the supply circuit of one of said electromagnets.

3. A device for controlling a hydraulic circuit as recited in claim 1wherein each of said end of travel switches are in series circuitarrangement with the contact in the supply circuit of one of saidelectromagnets.

4. A device for controlling a hydraulic circuit as recited in claim 1,wherein each of said second pair of switches is housed within a fluidtight housing mounted on said distributor.

References Cited UNITED STATES PATENTS 2,735,405 2/1956 Hipple 91-2752,736,296 2/1956 Romine et a1. 91-275 2,991,760 7/1961 Rhine 91--2753,060,466 10/1962 Kozacka 91275 3,225,541 12/1965 Piret 91-275 FOREIGNPATENTS 551,765 11/ 1956 Italy.

PAUL E. MASLOUSKY, Primary Examiner US. Cl. X.R. 91361, 466

